Climbers and officials in Nepal are worried that global warming is making the glacial environment unsafe for humans in the Himalayas.

They say human settlements and activities such as mountaineering are threatened by glaciers retreating and glacial lakes growing both
in number and size.

As the effects of climate change become ever more visible in the central Himalayas, Nepal's mountain community is worried by the
rise in precipitation across the region, including popular destinations such as Mount Everest and the Annapurnas.

Ang Tsering Sherpa, the president of the Nepal Mountaineering Association, says expedition teams are facing new hazards en route to the peaks, which he believes are caused by global warming.

"We can clearly see that when we go to the mountains and observe the glaciers and lakes there."

Temperatures rising

Nepal is home to most of the world's highest mountains. Recent analysis of weather data suggests that global warming is real.

We haven't studied much except analysing satellite images, it's about time we did a fresh survey

Sandip
Chamling Rai, World Wide Fund

Average temperatures are rising annually at a rate of 0.06C in Nepal, according to the country's Department of Hydrology and Meteorology.

"Global warming rates in different parts of the country vary," says Saraju Baidya, a meteorologist at the department, which has been collecting data from around the country for 30 years.

"In the Himalayan region, we have found out that the rate of warming, on average at 0.12C, is higher than in many places."

He and his colleagues say climate change has caused glaciers in the northern Himalayas to retreat at a rate never seen before, posing the threat of 'glacial lake outburst floods' (Glofs).

Experts like Mr Baidya say there were hardly any glacial lakes in the Himalayas 50 or 60 years ago. Today, however, things have
changed.

Glacial lake flood risk

There is growing concern that an earthquake or excessive precipitation could prompt Glofs, washing away villages and destroying infrastructure such as hydroelectric plants and bridges along river basins.

Dig Tsho lake in Nepal - site of a 1985 flood

More worryingly, melting Himalayan glaciers could have a huge impact on water resources and river systems across Asia.

According to a recent inventory carried out by Nepal's International Centre for Integrated Mountain Development (Icimod) and the United Nations Environment Programme (Unep), there are 3,252 glaciers and 2,315 glacial lakes in Nepal alone.

Of them, 26 glacial lakes are considered to be potentially dangerous. A similar inventory of Bhutan found 677 glaciers and 2,674 glacial lakes, of which 22 are potentially dangerous.

Between 1977 and 1998, five Glof events occurred in Nepal, causing significant loss to infrastructure and human settlements.

Similar destruction has also been caused on a number of occasions in Nepal over recent decades by glacial lakes bursting in neighbouring Tibet.

At the Tsho Rolpa glacial lake in northern-central Nepal, a drainage project was completed a few years ago to prevent such risks.

Experts say more action is needed now.

"We haven't studied much except analysing satellite images, it's about time we did a fresh survey and prepared an inventory," says Sandip
Chamling Rai at the Climate Change department of the World Wide Fund's Nepal programme.

Arun Shrestha, a climate change specialist at Icimod, adds: "Equally important is ground verification of the sites. Only then only we can take mitigation measures."